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. 2022 Oct 28;7(10):3094-3101.
doi: 10.1021/acssensors.2c01511. Epub 2022 Sep 19.

Organic Vapor Sensing Mechanisms by Large-Area Graphene Back-Gated Field-Effect Transistors under UV Irradiation

Katarzyna Drozdowska  1 , Adil Rehman  2 , Pavlo Sai  2 , Bartłomiej Stonio  2   3 , Aleksandra Krajewska  2 , Maksym Dub  2 , Jacek Kacperski  4 , Grzegorz Cywiński  2 , Maciej Haras  2   3 , Sergey Rumyantsev  2 , Lars Österlund  5 , Janusz Smulko  1 , Andrzej Kwiatkowski  1
Affiliations

Organic Vapor Sensing Mechanisms by Large-Area Graphene Back-Gated Field-Effect Transistors under UV Irradiation

Katarzyna Drozdowska et al. ACS Sens. .

Abstract

The gas sensing properties of graphene back-gated field-effect transistor (GFET) sensors toward acetonitrile, tetrahydrofuran, and chloroform vapors were investigated with the focus on unfolding possible gas detection mechanisms. The FET configuration of the sensor device enabled gate voltage tuning for enhanced measurements of changes in DC electrical characteristics. Electrical measurements were combined with a fluctuation-enhanced sensing methodology and intermittent UV irradiation. Distinctly different features in 1/f noise spectra for the organic gases measured under UV irradiation and in the dark were observed. The most intense response observed for tetrahydrofuran prompted the decomposition of the DC characteristic, revealing the photoconductive and photogating effect occurring in the graphene channel with the dominance of the latter. Our observations shed light on understanding surface processes at the interface between graphene and volatile organic compounds for graphene-based sensors in ambient conditions that yield enhanced sensitivity and selectivity.

Keywords: UV irradiation; acetonitrile; chloroform; fluctuation-enhanced sensing; graphene sensor; organic vapors; tetrahydrofuran.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Schematic representation of the investigated GFET (left panel) structure with the proposed sensing analysis (right panels).
Figure 2
Figure 2
Confocal optical microscopy image of a GFET. The magnified image on the graphene channel reveals a significant number of point and edge defects.
Figure 3
Figure 3
DC resistance RS of the back-gated GFET sensor between the drain and source as a function of gate voltage VG (a) for different gases in the dark and under UV irradiation (275 nm), and (b) a close-up for tetrahydrofuran, which shows how the UV light shifts both sensor resistance and gate voltage. The black dashed curve refers to the curve for tetrahydrofuran at UV (275 nm) after the shift by ΔRS and ΔVG marked by black arrows.
Figure 4
Figure 4
Power spectral density of voltage fluctuations SV(f) normalized to VS2 and multiplied by f for a GFET sensor, where VS is the DC voltage and f is the frequency. Plots (a) and (b) show the spectral range between 0.5 Hz and 500 Hz for dark conditions and under UV irradiation, respectively.
Figure 5
Figure 5
GFET sensor aging process after 7 days of exposure to chloroform vapor without intermittent cleaning of the sensor: (a) DC resistance RS at gate voltage VG = 60 V and (b) normalized power spectra SV(f)/VS2 × f of power spectral density of voltage fluctuations SV(f) for the GFET sensor with DC voltage VS across its terminals as a mean value taken in the frequency f range of 60–90 Hz. The error bars in (b) present the standard deviation from the mean value. Results designated as 0 day refer to measurements conducted for the sensor just after the cleaning procedure described in the Methods section.
Figure 6
Figure 6
GFET refreshing process using UV irradiation under N2 ambient: (a) DC resistance RS vs gate voltage VG characteristics for different times of refreshing process and (b) normalized noise spectra product SV(f)/VS2 × f collected before, during, and after sensor refreshing for a total of 100 min.
See this image and copyright information in PMC

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